My U.S. Pat. No. 4,426,097 discloses a small trailer adapted for attachment to a vehicle, the trailer utilizing a single caster-type wheel for support. This one-wheel trailer, and its stable and secure attachment to the vehicle, necessarily requires a special trailer hitch arrangement which, in the aforesaid patent, involves a T-shaped support having a longitudinally extending leg which attaches to a conventional vehicle drawbar, with a transversely extending leg having a pair of hitch balls adjacent the opposite ends thereof for attachment to dual couplers associated with the tow bar of the trailer.
While the single-wheel trailer and hitch arrangement of the aforesaid patent does operate in a desirable manner, and does provide desirable advantages particularly when backing a vehicle since the trailer tracks with the vehicle, nevertheless the American public has an inherent distrust of single-wheel trailers, apparently due to the public's inability to accept that such single-wheel trailers can be safely utilized. The only problem with such single-wheel trailers, however, is their limited load capacity, which capacity is limited by the suspension associated with the single caster-type wheel.
The public's lack of faith in single-wheel trailers is evidenced by the extensive use of two-wheel trailers. While most two-wheel trailers involve a conventional pivot-type hitch such that the trailer does not identically track with the vehicle, particularly when backing up, nevertheless there have been attempts to provide a two-wheel trailer which will track with the vehicle similar to a single-wheel trailer. For example, U.S. Pat. Nos. 2,475,174 (Boone), 3,033,593 (Zaha), 3,379,452 (Torrisi), 4,452,465 (Bourke), 4,305,602 (Ungvari), 4,512,593 (Ehrhardt) and 4,076,264 (Chatterley) all disclose two-wheel trailers employing some special arrangement, such as casters, a control linkage between the two caster wheels, and/or a dual or specialized hitch arrangement for effecting a rigid securement of the trailer to the towing vehicle. These latter patents have hence attempted to provide a structure so as to increase the control, and thus the tracking, of the trailer relative to the towing vehicle. These attempts, however, as evidenced by the complexities of the structures disclosed in these patents, and the fact that these structures still have undesirable characteristics, readily indicate the difficulty in providing a two-wheel trailer together with a hitch attachment therefore which will properly track with the vehicle movement, particularly when backing up.
More specifically, the aforementioned Boone U.S. Pat. No. 2,475,174 discloses a trailer having a pair of caster-type wheels, with the trailer having a single central hitch for attachment to the towing vehicle. The trailer also has a pair of separate auxiliary connectors disposed on opposite sides of the hitch adjacent the ends of the vehicle bumper, which auxiliary connectors control a flexible cable linkage, which in turn controls the swivelling of the casters. This patent hence discloses a three-point hitch arrangement, and does not permit free swivelling of the casters, but rather provides a complex arrangement for controlling swivelling of the casters.
The Zaha U.S. Pat. No. 3,033,593, as mentioned above, discloses a trailer having a pair of caster-type wheels, a central hitch of conventional configuration, and a pair of sidewardly spaced tie bars so as to create a three-point connection. This hence rigidifies the trailer relative to the vehicle, but the side tie bars must be released when swivelling of the wheels and backing of the trailer is desired. Further, this three-point connection does not permit proper rolling movement of the trailer relative to the vehicle, such as may be necessary to compensate for irregularities in the highway.
The aforementioned Ungvari U.S. Pat. No. 4,305,602 discloses a trailer having caster-type wheels, with the trailer having a dual hitch arrangement so as to rigidify the trailer relative to the vehicle. This double hitch arrangement, however, has several disadvantages. For example, the tow vehicle must be provided with a specialized tow bar which mounts hitch balls thereon. Further, the overall hitch arrangement does not permit or compensate for rolling movement of the trailer relative to the vehicle due to unevenness in the highway. This hitch arrangement also does not permit even weight distribution on the trailer or vehicle wheels.
The Ehrhardt U.S. Pat. No. 4,512,593, mentioned above, discloses two caster wheels joined together by drive sprockets and chains so that the caster wheels are constrained for simultaneous movement. The trailer also has two rigid tow bars which couple to sidewardly spaced hitch balls mounted on the tow vehicle. This arrangement possesses the same disadvantages mentioned above, and like Ungvari, does not permit relative roll between the vehicle and trailer.
Accordingly, it is an object of this invention to provide an improved hitch arrangement specifically for cooperation between a towing vehicle and a trailer of the type employing two caster wheels, which hitch arrangement provides improved tracking of the trailer and improved stability and load distribution on both the trailer and vehicle, while at the same time overcoming the disadvantages associated with prior hitch arrangements which have been associated with trailers employing caster wheels.
More specifically, the improved hitch arrangement, in combination with the two caster wheel trailer, provides a substantially rigid longitudinal connection between the vehicle and trailer so as to permit the trailer to be readily backed up while tracking with the vehicle, and at the same time the hitch arrangement provides not only relative hinging between the trailer and vehicle in a horizontal transverse direction so as to compensate for changes in road pitch or elevation, but it also permits roll of the trailer relative to the vehicle substantially about a longitudinally extending axis so as to compensate for uneven or nonlevel road conditions or uneven loading.
The improved hitch arrangement employs a main T-shaped connector which has a leg thereof rigidly attached to the conventional tow bar as associated with the vehicle, whereby the head of the connector extends transversely in substantially parallel relationship to the rear vehicle bumper. The head of the T-shaped connector swivelly supports thereon a roll pin which has the axis thereof extending substantially in the longitudinal direction of the trailer-vehicle combination. The roll pin projects rearwardly and is fixed to a trailer connector bar, the latter extending generally parallel to but spaced slightly rearwardly from the head of the T-shaped connector and also being swivably movable about the roll axis. This connector bar has a pair of conventional hitch balls mounted adjacent the opposite ends thereof for engagement with a pair of conventional ball-receiving couplers mounted on a pair of projecting tongues associated with the trailer. These tongues are fixed to and comprise part of the frame of the trailer, and have the connectors at the forward ends thereof spaced apart by a relatively small transverse distance, such as in a range of about 9 to 20 inches. The tow bars, as they project rearwardly from the couplers, diverge outwardly with respect to one another so that the longitudinal axes of the tow bars effectively intersect the vertical swivel axes of the caster wheels, whereby this facilitates the transmission of force from the ground through the wheels and trailer frame to the hitch arrangement.
Other objects and purposes of the invention will be apparent to persons familiar with arrangements of this general type upon reading the following specification and inspecting the accompanying drawings.